Four Js Development Tools Forum

Hello everyone.

I've already raised this issue with support and they say it's the expected behavior. I'd like to hear what the community has to say :)

When using the method util.JSONObject.fromFGL(rec) all DATE fields in rec (if any) are converted to the format "YYYY-MM-DD" regardless of the setting in DBDATE. This is also mentioned in the documentation. Consider this code:

IMPORT util
MAIN
DEFINE js util.JSONObject
DEFINE r record 
 date_element DATE 
END RECORD
DEFINE date_variable DATE
LET r.date_element  = TODAY
DISPLAY "r.date_element=",r.date_element 
LET js = util.JSONObject.fromFGL(r)
DISPLAY "JSON 2 string:", js.toString()
LET date_variable = js.get("date_element") 
DISPLAY "date_variable=",date_variable
DISPLAY "JSON type=",js.getType("date_element")
END MAIN
 

Displays:

r.date_element=28.11.2019
JSON 2 string:{"date_element":"2019-11-28"}
date_variable=     
JSON type=STRING

The simple .get() method returns the date_element as a string and  NULL is assigned to the date_variable, because the date is incorrect according to DBDATE setting.

As JSON itself knows nothing about dates the question arises: Why does FGL enforce DATE in JSON to be at a specific, hard-wired format rather than just DBDATE?

Best regards,
-Snorri

Hello Snorri,
your using the phrase "hard-wired format". I would argue differently: any util.JSON* method converting date to string (or vice versa) assumes dates are formatted according to the ISO 8601 date format. This fit's the real live.

Try this:
{code}
    LET date_variable = util.Date.parse(js.get("date_element"), "YYYY-MM-DD")
{code}

We should eventually add specialized get methods,
{code}
    LET date_variable = js.getDate("date_element")
{code}

Rene

Hello Snorri,
your using the phrase "hard-wired format". I would argue differently: any util.JSON* method converting date to string (or vice versa) assumes dates are formatted according to the ISO 8601 date format. This fit's the real live.

Try this:

LET date_variable = util.Date.parse(js.get("date_element"), "YYYY-MM-DD")

We should eventually add specialized get methods,

LET date_variable = js.getDate("date_element")

Rene

Hi Rene and thanks.

My problem with this is the fact that I was trying to use the JSONObject as a way to pass data to and from "generic" functions. As "DATE" is not a known JSON datatype, I have no way of knowing if the STRING I get using the .get() method is a DATE or not.  So in my "generic" routine this will fail:

call mydialog.setFieldValue("datefield", js.get("datefield"))

It will silently assign null to "datefield".

This works fine with all numeric and string  datatypes but I guess I will need to apply some conversions to boolean and datetime as well :(

I have a workaround where I use base.typeinfo.create() rather than util.JSONObject.fromFGL() and then I store the datatypes in a different structure. Then I covert the DATEs to ISO format before putting them back into the JSONObject structure (so the calling program can use .toFGL()). I could also probably get the datatype from the form, but all this is a lot of hassle.

Best regards,
-Snorri

Snorri,

In researching I came across this thread https://stackoverflow.com/questions/10286204/the-right-json-date-format which includes the answer because XKCD says so https://xkcd.com/1179/ :-)

By using ISO-8601 we should be good with using JSON to pass arguments to WebComponents

therein lies the problem, we don't know either


Boolean is a JSON data-type so shouldn't be a problem.  Datetime I'd expect us to use ISO-8601 as well but a quick check I don't see any T or Z in our output.  I am not 100% sure on the standard if Z,T mandatory or optional but I can imagine if we output "2019-12-04T09:00:00Z" instead of "2019-12-04 09:00:00" then that would cause a similar issue to what you are encountering with DATE, but for now (fortunately as it maybe we don't put T or Z into the datetime string) seems to be ok.  Also interestingly with numbers being a JSON data-type, I experimented with DBFORMAT and that does handle case of being able to assign appropriately (I tried with DBFORMAT using , as decimal point)

That point with datetime reminded me of the options we have with XML Serializer http://4js.com/online_documentation/fjs-fgl-manual-html/#fgl-topics/r_gws_XmlSerializer_option_flags.html.   It maybe that what you want is a similar option with JSON serialization ie use DBDATE or ISO-8601 with JSON serialization

Finally I also want to make sure that it is understood that with

LET date_variable = js.get("date_element")

js.get is returning a string in that instance.  So you have

LET date_variable = string

and the normal string to date conversion is taking place.  And as you discover the date in ISO-8601 format is not converted.

With util.JSONObject.toFGL as in

CALL js.toFGL(r)

http://4js.com/online_documentation/fjs-fgl-manual-html/#fgl-topics/c_fgl_ext_util_JSONObject_toFGL.html

that is effectively passing the data-type across and so has that information so as to parse the information.

Reuben
 

Thanks Reuben.


I think this is a great idea. Then you could toggle the behavior depending on what you are trying to achieve. Can you create a feature request? :)

BTW: I did not play with DBFORMAT, but js.get("integer_field") actually added ".0" at the the end. So with this JSON record:

{"i":123,"c":"Some data","d":789190.02}

DISPLAY js.get("i")

will display "123.0"

Best regards,
-Snorri